Vermiculite is the favorite material for loose fill insulation and by its very nature varies in size and shape of granules , and being just slightly squashy can easily form a blockage unless the material is guided into the pickup tube in an orderly manner . This may be considered a problem , but main users are DIY enthusiasts who do not really measure their time . The task can be done by unskilled labour ie. wives or girlfriends ......It can take an hour or two to feed a 100 litre bag of vermiculite into a normal ceiling ie. 8 foot overhead.......
Recycled and treated newspaper is the other main loose fill insulation available in the U.K. . and the degree to which blockages are prevented depends largely on how well the compressed paper 'fluff' is broken up into an even texture..